I struggle to find to the words to express just how absurd this sounds to me. I must be getting old.
Other things that were great, and I now miss---vaccum tubes in offices. Sure you don't need them to send messages, but if you want to send anything physical, however small, now you have to walk.
Oh and I certainly miss the bell system, where you could stand in the living room and ring a bell in any room in the house to tell the occupants that dinner was ready.
Most multi-handset cordless phones have a built-in intercom that will ring all the other handsets and establish a loopback call. But I bet not many people even have those any more ...
So, I would say this is not so much new as retro. True old-timers would recognize this use case right away.
The main use case I had in my mind is when my son is sleeping, shouting is undesirable. It would just be really convienent.
That said, I think the bigger problem would be triggering it to playback the recording - unless I'm missing something, they just respond to spoken commands.
Which would mean at best you could use it like a voicemail service: "Alexa, play me any messages sent from downstairs".
'My Cave is so big I can't even shout to the end. . . '
However, I would MUCH rather say "Alexia, tell upstairs that 'its time for dinner'", and it to be replayed upstairs. Rather than walking into the next room and yelling up the stairs like a neanderthal.